European patents EP-167.258 and EP-223.238 describe catalytic cleavage processes, in which certain perfluoropolyethers are catalytically separated by heat, thereby obtaining products having a reduced molecular weight and the same chain structure as the starting products, in the form of mixtures of compounds with both neutral and acid end groups. There are utilized fluorides and oxyfluorides of transition metals such as Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Mo, Zn, or of Al, Sn, Sb or precursors thereof, such as bromides, chlorides, oxides (which convert into the fluorinated catalytic species under the process conditions) operating at temperatures ranging from 150.degree. C. to 380.degree. C.
the cleavage can occur at the C-O bond of perfluoropolyethers, thereby obtaining more homogeneous and stable products with high yields (EP-167,258); the cleavage can also take place in chemically stabler points of the chain, if more effective catalyst and high temperatures are used (EP-223,238), operating under heavier products distillation and recycle conditions (EP-223,238).
Nevertheless, the residence times in the reactor are generally such that the substrate can undergo undersirable fragmentations prior to its extraction from the reactor, which are due, in particular, to the cleavage of the end groups, which give rise to gaseous products. Furthermore, the total specific productivity, i.e. the product amount per reaction time unit and per catalyst weight unit, and the duration of the catalyst life are not always satisfactory.
Thus, it was desirable to have available high-efficiency catalysts, such as to permit to increase the reaction rate without having to extend the times of contact with the catalyst, thereby avoiding the main cause for the undesired decomposition reactions which lead to the formation of gaseous products.